A process for producing a cigarette filter material

ABSTRACT

Filter materials for filtering aerosols, such as cigarette filters for filtering tobacco smoke, are provided comprising rigid polyurethane particles devoid of any cellular structure. Preferably the particles are granular and of jagged, spiny, cragged nature. The rigid polyurethane is produced from a polyol and a polyisocyanate. The particles are produced by first preparing a rigid polyurethane foam, preferably with the aid of a blowing agent, granulating the foam, treating the granules with hot water or steam to hydrolyze unreacted isocyanate and other free materials to render them inert, and then dried. Preferably, inorganic additives may be present during the preparation of the rigid polyurethane foam, such as the lower alkyl silicates, e.g., ethyl silicate, and water soluble salts of the acids of metals of groups VA and VIA of the Periodic Table, e.g., sodium tungstate. Inorganic additives may be added to the filter particles, such as an alkaline earth metal carbonate, silicate or hydroxide.

United StatesPatent n91 Strickman 45 Feb. 27, 1973 PROCESS FOR PRODUCINGA CIGARETTE FILTER MATERIAL [75] Inventor: Robert L. Strickman, RiverVale,

[73] Assignee: The Robert L. Strickman Foundation, Inc., New 'York, NY.

[22] Filed: June 16, 1970 [21] Appl. No.: 57,842

Related US. Application Data [60] Division of Ser. No. 721,563, April11, 1968, Pat.

No. 3,618,618, which is a continuation-in-part of Ser. No. 559,495, Dec.6, 1966, abandoned, which is a continuation-in-part of Ser. No. 424,626,Jan. 11, 1965, abandoned, which is a continuation-in-part of Ser. No.59,035, Sept. 28, 1960, abandoned.

[52] US. Cl. ..260/2.5 BD, 131/107, 131/265, 131/269, 260/25 A, 260/25AB, 260/25 AD, 260/25 AK, 260/25 BD [51] Int. Cl. ..C08g 22/44 [58]Field of Search ..260/2.5 A, 2.5 BD, 2.5 AK, 260/25 AD, 2.5 AB;l31/10.7, 265, 269;

[56] References Cited UNITED STATES PATENTS 3,120,849 2/1964 Guttag..260/2.5 AR 3,127,373 3/1964 Guttag ..260/2.5 AR

2,770,241 11/1956 Winkler... ..13l/265 3,538,020 ll/1970 Heskett....260/25 AK 3,574,150 4/1971 Jefferson..... 260/25 BD 3,171,820 3/1965Volz ....260/2.5 BD 2,181,614 11/1939 Stn'efling. ..131/265 3,006,34610/1961 Golding ..131/265 2,916,464 12/ 1959 Ebneth ..260/2.5 AB

FOREIGN PATENTS OR APPLICATIONS 922,306 3/ 1963 Great Britain ..260/2.5AK 620,248 5/1961 Canada ....26 0/2.5 BD 1,173,449 12/1969 Great Britain..13l/265 Primary Examiner,Donald E. Czaja Assistant Examiner-C. WarrenIvy Attorney-Louis F. Reed 57 ABSTRACT Filter materials for filteringaerosols, such as cigarette filters for filtering tobacco smoke, areprovided comprising rigid polyurethane particles devoid of any cellularstructure. Preferably the particles are granular and of jagged, spiny,cragged nature. The rigid polyurethane is produced from a polyol and apolyisocyanate.

'The particles are produced by first preparing a rigid' polyurethanefoam, preferably with the aid of a blowing agent, granulating the foam,treating the granules with hot water or steam' to hydrolyze unreactedisocyanate and other free materials to render them inert,

and then dried.

Preferably, inorganic additives may be present during the preparation ofthe rigid polyurethane foam, such as the lower alkyl silicates, e.g.,egyl silicate, and water soluble salts of the acids 0 me s of groups VAand VIA of the Periodic Table, e.g., sodium tungstate.

Inorganic additives may be added to the filter particles, such as analkaline earth metal carbonate, silicate or hydroxide.

12 Claims, 3 Drawing Figures PAIENIED Firm 191a 37 8,5 2

SHEET 1 0F 2 A PROCESS which was a continuation-in-part of my thenpending application, Ser. No. 59,035, filed Sept. 28, 1960, nowabandoned.

This invention relates to filters for treating aerosols in general andthe like, and especially tobacco smoke, as from cigarettes, etc. Inparticular, it is directed to novel filter structures, novel methods ofeffecting filtration of the smoke; novel filtering materials orcombinations thereof, and novel cigarettes embodying said novel filterstructures; and said filtering materials.

The problem of filtering aerosols, such as tobacco smoke, especially thesmoke from cigarettes, has arrested the attention of many investigators.Such smoke is a highly complex product. It contains nicotine, tars,irritating substances and many other components. Although many proposalshave been advanced and teachings disclosed as to how the smoke can betreated in the restricted working space (the cubage) at the end of acigarette, no one has heretofore developed a filter which provides forcontrolled elimination of the undesirable constituents present in thesmoke stream without imparing the taste quality" of the smoke.

I have discovered that it is possible to provide filters with means foreffectuating the removal of the unwanted components of the smoke streamwithout imparing the taste quality or the sensation thereof. In fact,with the filter of the present invention I am able to provide forimprovement in the taste quality of the smoke.

Accordingly, it is among the principal objects of this invention toprovide filters or filtration systems suitable for use in treatingaerosols, and particularly within the restricted cubage available in acigarette, which will:

1. Remove substantial amounts of the tarry components;

2. Remove substantial amounts of thealkaloids, in-

cluding the nicotine;

In addition to this, the filtration reduces the moisture content and thetemperature of the smoke'stream, and

removes irritating substances from the gaseous phase of the smoke. Theseeffects are obtained while supplying the satisfying quality (taste,aroma) sought by the smoker.

In its fundamental aspects, the objects of this invention as abovementioned, as well as other objects, are achieved by a combination oftreatments of aerosols, such as smoke, so that the reduction in irritantaction, moisture content, and temperature and the removal (by chemicaland physical fixation) of the unwanted, undesirable components areachieved during the flow of the smoke stream through the filter of theinvention.

More particularly, the objects of this invention are achieved inconsequence of the following: the tarry and particulate components arecaused to be removed from the smoke stream by providing a highlysuitable surface on which these components may impinge; and may alsoinclude means for efiectuating adsorption and/or absorption and removalof some of the irritating undesirable gaseous components of a smoke. Thefilter may contain surface activating substances which aid in removingunwanted substances from the smoke. The alkaloids, e.g., nicotine, etc.and other components of the smoke may be removed by suitable chemicalaction through the presence of substances which enter into chemicalcombination therewith, thus producing compounds that are retained by thefilter structure.

It is known that the irritating action or otherwise undesirable effectof tobacco smoke is due at least in part to the presence in the gasphase of such compounds as aldehydes, sulfides and hydrogen cyanide. Thefilter of the invention will remove substantial amounts of thesematerials. In addition, phenols and acidic materials which are known tobe present in tobacco smoke and are believed to be harmful are reducedin substantial amounts.

The filter of the invention therefore provides: means for extensivephysical and chemical processing of the smoke stream, including controlof the pH by removal of acidic components; fixation or binding of thealkaloids; and means for reducing the temperature of the smoke streamduring the flow through the filter to provide for temperature reductionto within a suitably desired range.

A fuller understanding of the foregoing objects and of the inventionwill become apparent to those skilled in the art from the followingdetailed description, taken in connection with the accompanying drawingswherein:

FIG. 1 is an illustration of a cigarette, partly in section, showing theutilization of a filtration unit in accordance with one of theembodiments of this invention.

FIG. 2 is a cross section, taken on the line 2-2, of FIG. 1.

FIG. 3 is a photomicrograph (magnified times) of granular filtermaterial in accordance with a preferred embodiment of the presentinvention, showing the jagged, spiny, cragged structure of theparticles. This photomicrograph was taken after the filter material hadbeen used as a filter in smoking a cigarette and the smoke passedthrough the filter. A number of the particles which had successfullyremoved tarry materials from the cigarette smoke are shown to havedarkened as compared to the lighter nature of the other particles.

The filter material of the present invention comprises a particulaterigid polyurethane which is essentially devoid of cellular structureand, in a preferred embodiment, is composed of granules which are of ajagged, spiny, cragged nature. The filter material is essentially devoidof any components, such as residual unreacted isocyanates, which impartany undesirable taste of their own to the smoke passing through thefilter. Rigid polyurethanes, as contemplated by the invention, arecharacterized by their essential lack of elasticity and their ability tobe readily converted into small particles using conventional granulatingequipment. This is contrasted with soft polyurethanes which behave likeelastomeric materials and which cannot be particulated under thesecircumstances.

The particulate filter material of the invention is desirably of aparticle size which is preponderantly below about 750 microns, andpreferably preponderantly between about 150 and 600 microns. It has beenfound that a particle size between about 175 and 450 microns give bestresults, but variations may be desirable depending upon consumerpreferences.

The rigid polyurethanes which comprise the filter material of theinvention are those conventionally known to be the reaction products ofpolyisocyanates with polyols. The polyols employed as starting materialspreferably predominantly have functionality of at least three. Therigidity of the polyurethanes, as well recognized by the polymerchemist, depends upon the existence of crosslinks between the moleculesand cross-linking is obtained by employing starting materials having areaction functionally greater than two. Most commonly, this higherfunctionality is found in the polyol component, but more recentlypolyisocyanates have become commercially available having afunctionality greater than two.

Any polyol which, when reacted with a polyisocyanate, produces a rigidpolyurethane, may be employed, although for cigarette filter use itshould not impart any noticeable odor or taste to the smoke. Among thepreferred polyols are the polyether polyols, and especially the reactionproducts of alkylene oxides, preferably propylene oxides, withlow-molecularweight compounds having three or more hydroxyl groups, suchas glycerol, 1,2,6-hexanetriol, trimethylolpropane, pentaerythritol,methylglycoside, sorbitol, sucrose, etc. Glycols, such as polypropyleneglycol, etc., may be employed especially if used together with a higherfunctional polyol or a polyisocyanate having a functionality of greaterthan two, i.e., having more than two isocyanate groups per molecule.

Instead of polyether polyols, there may be employedpolyhydroxyl-terminated polyesters, preferably those derived at least inpart from triols or higher. The polyester polyols are usually lessadvantageous than the polyether polyols because they are generally moreexpensive and more viscous.

Polyols are usually referred to in terms of their hydroxyl number.Polyols having a high hydroxy number (above 300) are preferred,particularly if polyols other than simple, non-polymeric polyols areemployed. Hydroxyl numbers which are between about 300 and 800 are mostdesirable. At the higher hydroxyl numbers, a more friable, but also amore dimensionally stable expanded polyurethane results.

Among the additional polyols which may be employed with a polyisocyanateto produce the rigid polyurethanes are: polyethylene glycol havingmolecular weights not exceeding 400, diethylene glycol, triethyleneglycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol,hexanediol, neopentyl glycol, trimethylolethane, trimethylolphenol,glucose, degraded starches and celluloses, hydroxymethyl derivatives ofcyclohexanol, castor oil, hydroxyl terminated polymers such as thosederived from lactones, such as caprolactone. These may be employedalone, or preferably as the reaction products with an alkylene oxide,such as propylene oxide, or with a polybasic acid or its anhydride.Among the polybasic acids which may be used are phthalic acid, adipicacid, sebacic acid, dimerized linoleic acid, oxalic acid and chlorendicacid.

Any polyisocyanate may be employed which will give a rigid polymer witha suitable polyol, but preferably any polyisocyanate which is a liquidat the temperature of reaction, i.e., at between about 15 C. and C. andparticularly between about 15 C. and 50 C. shall be employed.Particularly useful is the widely used tolylene diisocyanate (TDI) soldcommercially as the 80:20 mixture of 2,4:2,6 isomers, its crude grade,also p,p'-diphenyl methane diisocyanate (MDI) and its crude grade (PPI)and polymethylene polyphenyl isocyanate (a mixture sold under thetradename PAPl). Other polyisocyanates which can be employed are:dianisidine diisocyanate, xylylene diisocyanate, diphenyl sulfonediisocyanate, 4-chloro-1,3-phenylene-diisocyanate;4-isopropyl-l,3-phenylene diisocyanate; 2,4- diisocyanatodiphenylether;3,3-dimethyl-4,4-diisocyanatodiphenylmethane; mesithylene diisocyanate;4,4-diisocyanatodibenzyl; l,5-naphthalene diisocyanate;3,3-bitolylene-4,4'-diisocyanate; triphenylmethane triisocyanate,tritolylmethane triisocyanate, tetramethylene diisocyanate;hexamethylene diisocyanate; the diisocyanate derived from dimer acids;decamethylene diisocyanate, the reaction product of toluene diisocyanatewith trimethylolpropane at an NCO/OH ratio of 2:1 (Mondur CB), etc.

The polyisocyanate is advantageously employed in slight stoichiometricexcess over the polyol so as to provide excess isocyanate linkages forcross-linking with formation of biuret and allophanate linkages.However, typical isocyanate to organic hydroxyl group ratios are from0.75 to 1.25. On a weight basis this represents a range of approximately40 to 150 parts of polyisocyanate per parts of polyol. Excess isocyanatewill also react with any water, if present, to generate carbon dioxidewhich is a blowing agent to aid in forming a foam. Higher ratios up to 2or higher may be employed if water is present in the foaming reaction.The use of excess isocyanate as well as the use of polyisocyanate havingfunctionalities greater than two tend to provide foams which are morefriable.

The use of catalysts to assist in the formation of the polyurethane isconventional and may be employed in the present invention. Catalystswhich are water soluble and which, therefore, may be removed from thereaction product by water washing are preferred. Since the products areintended for use in cigarette filters, it is also desirable that thecatalyst be substantially odorless and imparts no taste to the smoke.Especially effective as a catalyst isN,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (sold under thetradename Quadrol), since it is both catalytic, because of its aminogroups, and reactive with the polyisocyanate, because of its hydroxylgroups. It acts, therefore, as a polyol, a catalyst and a crosslinkingagent and since it becomes chemically incorporated into thepolyurethane, it imparts no odor to the final product or taste to thesmoke. Such amines as bis-(2-hydroxypropyl)-2-methylpiperazine anddiethanol amine behave similarly.

Catalyst may be omitted, especially of the formulations of Examples 3and 4, below, are employed. If a conventional catalyst is employed,amounts of between 0.02 and 2.0 parts per 100 parts by weight of polyolare desirable, but if Quadrol or other catalyst which becomes chemicallyincorporated into the polymer is employed, much larger amounts, such asup to 20 parts, are usually desirable.

Instead of the catalyst disclosed above, any of the conventional basiccatalysts employed in polyurethane foam technology can be used. Theseinclude N-methyl morpholine, N-ethyl morpholine, trimethylamine,triethylamine, tributylamine and other trialkylamines, tetramethylbutanediamine, trimethylpiperazine, tetramethylguanidine, diethylaminoethanol,3- diethylaminopropionamide, heat activated catalysts, such astricthylamine citrate, 3-morpholinopropionamide, Z-dithylaminoacetamide,the esterification product of 1 mole of adipic acid and 2 moles ofdiethylethanolamine, triethylenediamine, N,N-diethylpiperazine,N,N-dimethylhexahyroaniline and tribenzylamine. Tin catalysts may alsobe used alone or in conjunction with amine catalysts. They includestannous octoate, dibutyltin acetate, dibutyltin dilaurate, dibutyltindioctoate, etc.

The polyurethane is produced first in an intermediate form as a rigidfoam. This foam may be produced in accordance with the practices wellknown in the foam art as the prepolymer method, the semiprepolymer (orquasi-prepolymer) method, or the socalled one-shot method. These are allwell-known methods of foam preparation. The semi-prepolymer method isgenerally considered to be more reliable, but the one-shot method isclearly the more economical. Both of these latter two methods areespecially suitable for manufacture of the foam from which filtermaterial of the present invention may be produced.

The preparation of foam requires the preparation of polyurethane in thepresence of some means of blowing or expanding the polymer material. Inaccordance with one well-known foam-producing technique water may beemployed which will react with excess isocyanate to produce carbondioxide from the reaction, which then acts as the blowing or expandingagent. One may employ nitrogen or carbon dioxide gases to provide theexpansion. Also, whipping of air into the polymerizing mass may be used.In accordance with one preferred method of the invention, it isdesirable to employ a halogenated hydrocarbon, such as the fluorinatedhydrocarbons of the type sold under the trademarks Freon and Genetron."Among the fluorinated hydrocarbons which may be employed are those whichare sufficiently volatile to evaporate at the temperature of foamproduction. Desirably, the material shall have a boiling point slightlyhigher than ambient temperature. Among the satisfactory fluorinatedhydrocarbons which may be employed are trichlorofluoromethane,dichlorodifluoromethane, dichlorotetrafluoroethane,dichloromonofluoromethane, monochlorodifiuoromethane,trichlorotrifluoroethane, and monochlorotrifluoromethane. Desirably,about 5 to 35 parts of blowing agent are employed per 100 parts ofpolyol.

Conventional surface active agents may be employed, especially thoseknown to polyurethane technologists, to help in nucleation and theformation of a more or less uniform, fine cell structure. These includethe silicones and particularly those known in the trade as L-520, L-530,L-53l0, and L-5320 (Union Carbide) and DC-l99, DC-l13, DC-l and'DC-202(Dow Corning), XF-l066 (General Electric) believed to be blockcopolymers of silicone and alkylene oxides. These are usually employedin amounts of up to 1 part per 100 of polyol.

The rigid polyurethane foam is cured after formation by being permittedto stand at ambient temperature for at least about a day. Alternatively,the curing may be accelerated by the use of elevated temperatures, whichgenerally should not exceed 130 C. During the curing treatment the foamloses its tackiness and develops its maximum rigidity.

After the rigid polyurethane foam is produced, the foam is subjected toa granulation operation to produce granular particles having highlyirregular physical shapes in the form of jagged, spiny, craggedparticles which characterize the invention. One preferred method ofgranulation is the use of a mill wherein impact and friction ofparticles impinging against one another causes a particulating action.One such mill is the Pallmann Model REF mill.

After the grinding operation, the rigid polyurethane particles aresubjected to the action of hot water or steam. This is an important partof the process. This is more than a simple washing operation since, inaddition to removing soluble components, it also provides a chemicalreaction to convert residual isocyanate, which is irritating to themucous membranes, and any ethyl silicate which may be present from atreatment which will be described hereinbelow, into odorless products ofnegligible vapor pressure. This is a hydrolysisreaction and one which isparticularly important for filter material of the invention to beemployed in the filtration of cigarette smoke. The hydrolysis istypically conducted at temperatures of about 50 to 100 C., andpreferably between about and C. Higher temperatures such as achieved byautoclaves or the use of steam may be employed, provided they do notdegrade the jagged, spiny character which defines the preferredembodiments of the invention. It is important to allow sufficient timeto complete the step as I have found that an inadequately hydrolyzedproduct not only has a most disagreeable, irritating odor, but alsolacks the high smoke filtering capacity of my properly hydrolyzed filtermaterials.

It is desirable, although not essential, to employ certain materials inthe preparation of the rigid polyurethane foam which is an intermediatematerial in the preparation of the filter material of the invention.Thus, for example, it is desirable to employ water-soluble ate or acidsalts of metals of groups VA and VIA of the Periodic Table of Elements,such as the alkali tungstates, molybdates, vanadates and chromates. (Insome forms of the periodic table the metals tungsten, molybdenum,vanadium and chromium are referred to as being in groups VB and VIB).The preferred salt for this purpose is sodium tungstate. These metalsalts are employed in the form of their aqueous solutions, preferablyhaving a strength of about 10 to 30 percent by weight and an amountranging from 0.2 to 4 parts per 100 parts by weight of polyol, and,preferably, from about 0.5 to 2 parts per 100 parts of polyol, with thewater-soluble metal salt being used in aqueous solution having astrength of 20 to 30 percent.

These water-soluble salts may be omitted, but with a concomitantsacrifice in the speed of reaction in producing the polyurethane. Thesewater-soluble metal salts have been found to be extremely helpful inproducing low density foams. This is desirable since it is preferable toemploy as the rigid polyurethane foam inintermediate foam is the loweralkyl silicates, such as 10 those alkyl silicates containing up to fourcarbon atoms in the alkyl group. Ethyl silicate is preferred. It isdesirable to employ up to about 5 parts of alkyl silicate per 100 partsof polyol. Where ethyl silicate is employed, it is particularlyimportant to subject the reaction product before use to the hydrolysistreatment employing hot water or steam so as to hydrolyze any free ethylsilicate and thereby remove any toxicity or odor problems.

In accordance with a preferred embodiment of the invention it isdesirable to incorporate certain other in organic additives into theparticulate polyurethane filter material. Those inorganic additives,such as aluminum hydroxide and magnesium trisilicate, as well as othercarbonates, silicates or hydroxides of alkaline earth metals may beemployed. Thus one may employ magnesium hydroxide, magnesium oxide,magnesium carbonate, calcium carbonate, a gel of magnesium carbonate andaluminum hydroxide dried together, and magnesium aluminum silicate.Among these the mixture of aluminum hydroxide and magnesium trisilicatehas been found to give the most acceptable taste to smokers. Whenaluminum hydroxide and magnesium trisilicate are employed, they arepreferably added as a 1:1 mixture by weight in amounts of between about3 and percent by weight of the filter material. However, ratios of thetwo components may be varied materially and the total amount may varyfrom 0 to 25 parts by weight per 100 parts of polyurethane particles.These inorganic additives are believed to be particularly desirable toremove certain constituents from the gaseous phase of tobacco smoke andto make tobacco smoke milder by removing irritating compounds from thegas. Surprisingly, the filter material of the invention having theseinorganic additives present provides a highly selective removal ofnicotine from the smoke.

The particle size of the inorganic additives may be the same as for thepolyurethane particles or lower, for example, less than 750 microns.

Other additives which may be employed with the filter material of theinvention are cellulose acetate fibers, charcoal granules, powderedcellulose, etc. These materials should not exceed 25 percent by weightof the polyurethane filter material.

The following are examples in accordance with this invention. The partsare by weight, unless otherwise specified.

EXAMPLE 1 Step A A polyurethane foam was first manufactured from thefollowing materials:

100 parts of polyol (formed by the condensation of sorbitol withpropylene oxide, the condensation product having a hydroxyl number ofabout 490 (available as G 2410 from Atlas Powder Co., ChemicalsDivision, Wilmington 99, Delaware); 76 parts of tolylene diisocyanate (acommercially available 80/20 mixture of the 2,4 and 2,6 isomers);

25 parts of trichlorofluoromethane; and

0.5 to 1.5 parts of triethylenediamine, as catalyst.

The catalyst is dissolved in the halogenated hydrocarbon, which is addedto the polyol, followed by isocyanate and the mixture is suitableagitated. Foaming begins.

Upon completion of the foaming reaction, and when the mass becomesrigid, it is granulated. The granular mass, having a mesh size in therange of 50300 (U.S. standard mesh size), constitutes material forpreparation of a filter unit.

Step B The granular mass produced in Step A is washed with hot water forabout 3-5 minutes and filtered. This removes any free isocyanate. Thestill moist granules are dried at atmospheric pressure at a temperatureof 60l05 C., or if desired, under sub-atmospheric pressure, at a lowertemperature. The dried granules constituting the product of this Exampleare filled into the open tubular end of a cigarette and thus constitutea filter unit. The granules are prevented from falling out by a smallplug of cotton or other suitable material.

Such a structure is illustrated in FIG. 1 wherein l0 designates acigarette, 12 the tobacco, 14 the granules and 16 the plug.

EXAMPLE 2 80 to 97 parts of the dried isocyanate-free granules ofExample 1, and 3 to 20 parts of a 1:1 mixture of:

0. aluminum hydroxide and b. magnesium trisilicate are intimately mixed.This mixture, when filled into the open tubular end of a cigarette,constitutes a filter. The general structure thereof is akin to FIG. 1.

EXAMPLE 3 To 100 parts of the polyol described in Example 1, there areadded a blend of:

10 parts of a 20 percent sodium tungstate aqueous solution, and

10 parts of ethyl silicate (condensed, 40 percent SiO content).

To the mixture formed by the addition of the blend with the polyol,there are added:

76 parts of tolylene diisocyanate (described in Example l) and 25 partsof trichlorofluoromethane.

The mixture is allowed to react. Upon completion of the reaction andwhen it becomes rigid, it is granulated, washed and dried as describedin Example 1. Alternatively, the isocyanate may be reacted at about 80C. with a portion (about /4) of the polyol to form a quasiprepolymer.The latter is then reacted with the remainder of the polyol in thepresence of the blowing agent and catalyst. The foam thus produced has afine uniform cell structure. The product consists of spiny, jagged,craggy irregularly shaped particles with a large surface area.

The granules produced in this Example, when filled into the open tubularend of a cigarette, constitute a filter unit. The general structurethereof is akin to FIG. 1.

EXAMPLE 4 EXAMPLE 5 STEP A Step 30 parts of a reaction product ofpentaerythritol with propylene oxide and having a hydroxyl number of 560is mixed with 100 parts of tolylene diisocyanate (80/20 mixture of the2,4 and 2,6 isomers). The temperature is not allowed to exceed 90 C. andthe reaction is carried out under dry nitrogen gas. The product isallowed to cool and is stored in the absence of moisture.

Step B A mixture is made of 75 parts of the polyol described in Step A,parts of N,N,N',N'-tetra-kis (Hydroxypropyl) ethylene diamine, 3 partsof a 30 percent aqueous solution of sodium tungstate, 2 parts of ethylsilicate, 0.3 part of a 30 percent aqueous solution of triethylenediamine, parts of trifluorochloromethane, and 0.5 part of aurethanegrade silicone surface active agent (L-520 of Union Carbide).

Step C Approximately equal weights of the products from Step A and StepB are thoroughly mixed and poured into a mold. The resulting foam is awhite, fine-celled material which is allowed to cure for a day at roomtemperature. The resulting foam is granulated in a Pallrnann mill, andthe resulting particles treated with boiling water for about 15 minutes,followed by about a half hour at 80-l00 C. The treatment with water maybe repeated, if desired, and is continued until the product is odorfree. The white granules are then dried in an oven at 105 C. Thefraction smaller than 420 microns particle size and larger than 177microns particle size is collected. It consists of particles with aspiny, cragged, irregular shape devoid of cellular structure.

In lieu of sodium tungstate mentioned in the foregoing example, theremay be used potassium tungstate, or any alkali metal molybdate,vanadate, chromate, etc.

EXAMPLE 6 Example 3 was repeated, employing instead of tolylenediisocyanate an equivalent weight of methylene diphenyl diisocyanate.The result was a filter material having equivalent properties to thoseof the produce of Example 3.

EXAMPLE 7 Example 4 was repeated, but omitting the ethyl silicate. Theresulting material produced a satisfactory filter.

EXAMPLE 8 Example 4 was repeated, but employing an equal weight ofsodium vanadate instead of sodium tungstate. The resulting filterproduct was similar in its properties to the product of Example 4.

EXAMPLE 9 Example 4 was repeated, but employing an equivalent amount ofa mixture of polypropylene glycol (Niax 1025) and Quadrol instead of thesorbitol derived polyol. The resulting filter material was similar inits properties to the produce of Example 4.

EXAMPLE 10 Example 4 was. repeated, but employing an equivalent amountof polymethylene polyphenyl polyisocyanate (PAPI) instead of tolylenediisocyanate. The filter product obtained was similar in its propertiesto the product of Example 4.

EXAMPLE 11 Example 4 was repeated, but employing an equal weight amountof sodium molybdate instead of sodium tungstate. The resulting filtermaterial was similar in its properties to the product of Example 4.

EXAMPLE 12 Example 4 was repeated, but employing an equal weight amountof sodium chromate instead of sodium tungstate. The resulting filtermaterial was similar in its properties to the product of Example 4.

EXAMPLE 13 To the product of Example 3 was added 2.5 percent by weightof each of magnesium hydroxide and aluminum hydroxide. The resultingproduct was found to remove more tars and nicotine from cigarette smokethan the filter material of Example 3.

EXAMPLE 14 To the product of Example 3 was added 2.5 percent by weightof each of calcium carbonate and magnesium carbonate. The resultingproduct was found to remove more-tars and nicotine from cigarette smokethan the filter material of Example 3.

EXAMPLE 15 To the product of Example 3 was added 5 percent by weight ofaluminum hydroxide and 2.5 percent by weight of magnesium trisilicate.The resulting product was found to remove more tars and nicotine fromcigarette smoke than the filter material of Example 3.

EXAMPLE 16 To the product of Example 3 was added 12.5 percent by weightof each of aluminum hydroxide and magnesium trisilicate. The resultingproduct was found to remove more tars and nicotine from cigarette smokethan the filter material of Example 3.

EXAMPLE 17 To the product of Example 3 was added 5 percent by weight ofmagnesium aluminum silicate. The resulting product was found to removemore tars and nicotine from cigarette smoke than the filter material ofExample 3.

EXAMPLE 18 To the product of Example 3 was added 5 percent by weight ofcodried gel of magnesium carbonate and aluminum hydroxide. The resultingproduct was found to remove more tars and nicotine from cigarette smokethan the filter material of Example 3.

EXAMPLE 19 To the product of Example 3 was added percent by weight ofmagnesium oxide. The resulting product was found to be excellent for theremoval of tars and nicotine from cigarette smoke.

COMPARISONS Comparative tests were conducted by the method described byWartman, Cogbill and Harlow in their paper entitled Determination ofParticulate Matter in Concentrated Aerosols-Application to Analysis ofCigarette Smoke," Analytical Chemistry, Volume 31, pagesl705-09,0ctober, 1959.

Cigarette A This cigarette was a Kent, king size, with its usual filter.

TPM 17.5 mg; Nicotine =0.83 mg.

Cigarette B This cigarette was one whereof the filter unit consisted of65 mg. of shredded foam prepared by the shredding method described inExample 7 of Winkler U. S. Pat. No. 2,770,241.

The foam was made from one hundred parts of a polyester resin, acid No.35, made from 3 mols of adipic acid, 3-% mols of 1,4-butylene glycol and5; mol of glycerine, was copolymerized with 48 parts of a mixture oftolylene diisocyanate (the 2,4- and 2,6-isomers) in the presence of onepart of a 10 percent aqueous solution of a non-ionic emulsifier, AerosolOT, and A part of N-methyl-morpholine, as the activator. The mass wasmixed and placed into a preheated mold.

This highly elastic foam was shredded and 65 mg. thereof were packedinto a one inch long hull.

TPM 16.8 mg; Nicotine 0.79 mg.

Cigarette C This cigarette was one whereof the filter unit consisted of65 mg. of granules (14 of FIG. I) prepared as described in Part A ofExample I.

TPM 13.8 mg; Nicotine =0.73 mg.

Cigarette D This cigarette was one whereof the filter unit con- 5 sistedof 65 mg. of the granules 14 of FIG. 1) prepared This cigarette was onewhereof the filter unit consisted of 65 mg. of granules (14 of FIG. 1)prepared as described in Example 2.

TPM 10.2 mg; Nicotine 0.60 mg.

Cigarette F This cigarette was one whereof the filter unit consisted of65 mg. of the granules 14 of FIG. 1) prepared as described in Example 3.

TPM 9.8 mg; Nicotine 0.56 mg.

Cigarette G This cigarette was one whereof the filter unit consisted of65 mg. of the granules (14 of FIG. 1) prepared as described in Example4.

TPM 7.3 mg; Nicotine 0.51 mg.

In a series of panel tests, I have found that there was a marked andnoticeable diminution in the irritating effect and cough reflexes ofsmoke filtered in accordance with units of this invention as contrastedwith that of commercially available filter cigarettes.

In the preferred embodiment of this invention, 1 utilize as thefundamental component of the filter, granulated rigid polyurethanes asdescribed above which are characterized by the absence of free,unreacted isocyanate and of other materials which impart undesirabletaste to tobacco smoke. The filter materials of the invention exhibithigh surface energies which make them especially suited for adsorption.They also have an exceedingly large surface area and what is alsounusual, they possess an electrical charge. This latter phenomenon isshown by a strong tendency toward electrostatic effects.

It is also to be noted that filter units may be made by spreading thegranulated filter material, or mixtures of the granulated filtermaterial and aluminum hydroxide and magnesium trisilicate, on a sheet ofcigarette paper or other suitable thin cellulosic stock; rolling thesame; and cutting therefrom suitably sized plugs or cartridges. Theseplugs constitute suitable filter units.

Table 1, below, sets forth the filtration effects of filter units madein accordance with this invention as compared with those of filtercigarettes on the market. mgs. of a granulated material as prepared inExample 3 hereinabove was used in these comparisons.

TABLE 1 Filter Brand Brand filter removed and replaced with 150 mgs. offilter material of Example 3 Total Nicotine Total Nicotine ParticulateParticulate Matter Matter Mgs. Mgs. Mgs Mgs.

Pall Mall 26.9 1.51 10.9 .55 Chesterfield 26.4 1.14 10.7 .53 Marlboro26.0 1.36 7.9 .41 Lucky Strike 25.7 1.09 10.3 .53 Viceroy 23.4 1.34 6.7.39 Winston 23.3 1.28 9.9 .50 Lark 21.8 1.21 9.6 .34 Kent 17.2 .83 7.9.35 True 14.4 .74 6.6 .36 Carlton 10.6 .59 3.2 .20

The terms and expressions which have been employed are used asterms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimedis:

l. A process for producing a filter material for use in filtering anaerosol, which process comprises reacting a polyisocyanate and a polyolin amounts sufficient to provide a ratio of reactive isocyanate groupsto organic hydroxyl groups of between about 0.75 and 1.25 to produce arigid polyurethane, in the presence of sufficient blowing agent that therigid polyurethane shall be produced as a foam having a density of lessthan about 3 pounds per cubic foot, granulating the resulting rigid foamto produce granules essentially devoid of cellular structure and of ajagged, spiny, cragged nature, having a particle size of less than 750microns, subjecting the granules to a hydrolysis treatment with hotwater or steam, and drying the product.

2. A process in accordance with claim 1 wherein the polyisocyanate istolylene diisocyanate.

3. A process in accordance with claim 1 wherein between about 40 and 150parts by weight of polyisocyanate are employed for each parts of polyol.

4. A process according to claim 1 wherein the polyurethane is preparedin the presence of a water-soluble salt of an acid of a metal of GroupsVA and VIA of the Periodic Table of Elements.

5. A process according to claim 1 wherein the polyurethane is preparedin the presence of a water-soluble alkali salt of an acid of a metalselected from the class consisting of tungsten, vanadium, chromium andmolybdenum.

6. A process according to claim 1 wherein the polyurethane is preparedin the presence of a water-soluble alkali tungstate.

7. A process according to claim 4 wherein the amount of saidwater-soluble alkali salt employed is between about 0.2 and 4 parts byweight per 100 parts of polyol.

8. A process according to claim 1 wherein the polyurethane is preparedin the presence of a lower alkyl silicate.

9. A process according to claim 1 wherein the polyurethane is preparedin the presence of up to about 5 parts by weight of ethyl silicate per100 parts of polyol.

10. A process according to claim 1 wherein there is added to the driedproduct a member selected from the class consisting of alkaline earthmetal carbonates, silicates and hydroxides. I

11. A process according to claim 10, wherein said member-is added in anamount not exceeding 25 percent by weight of the dried product.

12. A process according to claim 1 wherein there 18 added to the driedproduct between about 3 and 15 percent by weight of an approximatelyequal parts mixture of aluminum hydroxide and magnesium trisilicate.

2. A process in accordance with claim 1 wherein the polyisocyanate istolylene diisocyanate.
 3. A process in accordance with claim 1 whereinbetween about 40 and 150 parts by weight of polyisocyanate are employedfor each 100 parts of polyol.
 4. A process according to claim 1 whereinthe polyurethane is prepared in the presence of a water-soluble salt ofan acid of a metal of Groups VA and VIA of the Periodic Table ofElements.
 5. A process according to claim 1 wherein the polyurethane isprepared in the presence of a water-soluble alkali salt of an acid of ametal selected from the class consisting of tungsten, vanadium, chromiumand molybdenum.
 6. A process according to claim 1 wherein thepolyurethane is prepared in the presence of a water-soluble alkalitungstate.
 7. A process according to claim 4 wherein the amount of saidwater-soluble alkali salt employed is between about 0.2 and 4 parts byweight per 100 parts of polyol.
 8. A process according to claim 1wherein the polyurethane is prepared in the presence of a lower alkylsilicate.
 9. A process according to claim 1 wherein the polyurethane isprepared in the presence of up to about 5 parts by weight of ethylsilicate per 100 parts of polyol.
 10. A process according to claim 1wherein there is added to the dried product a member selected from theclass consisting of alkaline earth metal carbonates, silicates andhydroxides.
 11. A process according to claim 10, wherein said member isadded in an amount not exceeding 25 percent by weight of the driedproduct.
 12. A process according to claim 1 wherein there is added tothe dried product between about 3 and 15 percent by weight of anapproximately equal parts mixture of aluminum hydroxide and magnesiumtrisilicate.